[sysrst_ctrl] Add combo loop waiver
[sysrst_ctrl] Add combo loop waiver

A combo loop path is seen as follows

key input -> sysrst_ctrl_inv -> key output, which then feeds back.

It seems like the inversion path is a known function of the design.
Since this inversion path works on muxed pins, we have no choice
but to use a waiver.

Signed-off-by: Timothy Chen <d7b2ae30d8c0f215facd721941273067fd1d14a2@google.com>

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